So it was heartening to read an article on Forbes highlighting exactly the same thing. They used mystery shopping to test more than 10,000 sales, and then studied uptake and actual sales conversion. The conclusion was simple, the faster you respond the more likely you are to close the sale. (Everything being equal)

Customers appreciate a fast response time. It gives them confidence that you value their business, and that this is how you’re going to be taking care of them when they start working with you.

Even if you don’t have some form of lead management system, respond to your email (inquiries) as quickly as you can, otherwise you’re probably missing out on a good chunk of business.